用心率变异性谱分析法研究振动性白指患者自主神经系统对冷刺激的反应

目的研究振动性白指患者的自主神经系统对冷刺激的反应。方法２２名振动性白指患者（ＶＷＦ组）及１９名正常对照（对照组）进行了局部冷水刺激实验,记录受试者的心电信号,实验后将记录的心电信号通过处理转化为ＲＲ间期信号,然后对这些ＲＲ间期信号进行功率谱分析,计算标准化的ＬＦ（０．０２～０．１５Ｈｚ）功量（ＬＦ％）,标准化的ＨＦ（０．１５～０．４０Ｈｚ）功量（ＨＦ％）,以及ＬＦ／ＨＦ比率。结果冷暴露开始后,ＶＷＦ组及对照组的ＨＦ％与暴露前的水平相比都有显著下降,ＶＷＦ组的ＬＦ／ＨＦ比率与暴露前的水平相比有显著增大,而且冷暴露中ＶＷＦ组的ＬＦ／ＨＦ比率显著高于对照组的相应的ＬＦ／ＨＦ比率。结论冷刺激导致ＶＷＦ组和对照组的副交感神经活动减弱,但对照组还能保持交感与副交感的平衡,而ＶＷＦ组却不能保持两者平衡,交感神经活动明显占优,冷刺激中ＶＷＦ组ＬＦ／ＨＦ比率明显高于对照组的ＬＦ／ＨＦ比率说明振动性白指患者的交感神经系统对冷刺激可能存在过敏反应。     

Spectral analysis of heart rate variability during exercise in trained subjects

PURPOSE: To investigate the effects of strenuous exercise on heart rate variability (HRV). METHODS: We evaluated the effects of exercise intensity and duration on HRV indices in 14 healthy trained subjects. Each subject exercised for 3, 6, and 9 min at 60 and 70% of the power achieved at maximal oxygen consumption (PVO2(max)) and for 3 and 6 min (or 3 min twice) at 80% of PVO2(max). The electrocardiogram RR intervals were recorded then processed by fast(FFT) and short-time (STFT) Fourier transform for determination of low-frequency (LF, 0.045-0.15 Hz) and high-frequency (HF, 0.15-1.0 Hz) components. RESULTS: The LF and HF components expressed as absolute power (ms2) decreased significantly at the onset of exercise (P < 0.05). However, with increasing exercise intensity, the HF component expressed as normalized units (n.u.) (reflecting parasympathetic modulation) increased significantly, whereas the LF component (n.u.) and LF/HF ratio (both reflecting sympathetic modulation) decreased significantly (P < 0.05). STFT showed that increasing exercise intensity was associated with a shift in HF peak frequency related to an increase in respiratory rate and a marked decrease in LF power (ms2). Moreover, HFn.u. rose (r = 0.918, P < 0.01) and LFms2 fell as minute ventilation increased (r = 0.906, P < 0.01). CONCLUSIONS: Parasympathetic respiratory control and nonautonomic mechanisms may influence the HF-peak shift during strenuous exercise. HRV and the usual indexes of sympathetic activity do not accurately reflect changes in autonomic modulation during exhaustive exercise.     

Effects of exercise load and breathing frequency on heart rate and blood pressure variability during dynamic exercise.

It is known that heart rate (HR) variability decreases with dynamic exercise, but there are only few studies on blood pressure (BP) variability with exercise loads and the effect of breathing pattern has never been investigated. Thus, we studied HR and systolic blood pressure (SBP) signals by spectral analysis (FFT), in 9 healthy subjects, at different breathing frequencies (0.15, 0.2, 0.3, 0.4, 0.5, 0.6 Hz), at rest and during 3 exercise loads (25, 50 and 75% VO2max). BP was measured with a non-invasive device (Finapres) and continuously recorded. The power spectrum of R-R period significantly decreased with exercise loads in the low frequency band (LF: 0.04-0.128 Hz) and in the high frequency band (HF: 0.128-0.65 Hz), but with breathing frequency only in the HF part of the spectrum. The power spectrum of SBP significantly increased with exercise loads in LF and HF bands, and decreased in HF band with increasing breathing frequency. R-R and SBP HF peaks were centered on breathing frequency peaks. Therefore, spectral analysis of HR and SBP confirm the withdrawal of vagal control during exercise, while mechanical effect of respiration on SBP persists. LF/HF ratio of R-R spectral components decreased with increasing load, whereas cardiovascular sympathetic activity is known to rise, suggesting that this ratio is not a good indicator of cardiovascular autonomic modulation during exercise.     

Heart rate variability during high-intensity field exercise in female distance runners

The purposes of this study were to demonstrate the transition of heart rate variability (HRV) during trials in the field and to examine the relationship between peak frequency of high-frequency band (HF) and stride frequency. Ten healthy long-distance college female runners (age 19-21 years) performed a 3000 m realistic time trial. The time-series power spectrum analysis by maximum entropy method was used to evaluate cardiac autonomic nervous activity during the race. Cross-correlation coefficients were calculated to estimate the degree of linear co-ordination between the central peak frequency of HF and stride frequency. Just after starting, the decrease in HF (0.15-1.00 Hz) and a transient increase of low-frequency band (LF)/HF were found. After that, the HF remained at a low level and LF/HF decreased sharply. These findings suggested that the parasympathetic activity was suppressed and sympathetic activity increased just after starting, and the sympathetic activity reached the saturated level according to continuation of high-intensity exercise. In spite of the significant decrease of HRV during trials, peak frequency of HF could be differentiated clearly. The cross-correlation coefficient of peak frequency of HF and stride frequency was from 0.703 to 0.868. This finding indicated that exercise rhythm reflected HRV during high-intensity running in the field.     

Intense endurance training on heart rate and blood pressure variability in runners.

Physical training with incomplete recovery times can produce significant fatigue. A study of cardiovascular responses showed that there is a sympathetic and a parasympathetic form of fatigue. PURPOSE: The purpose of this experimentation was to measure the effects of intense endurance training on autonomic balance through a spectral analysis study of the heart rate (HR) and systolic blood pressure (SBP). METHODS: Eight elite runners were tested twice: after a relative rest period (RRP) of 3 wk and after an 12-wk intense training period (ITP) for endurance. At the end of each phase, the subjects were tested by means of a VO2max test and a tilt-table test. RESULTS: The resting heart rate (HR) variability was lower (P < 0.001) in the intensive training phase. Likewise, there were differences in the low-frequency (0.04-0.150 Hz; LF) and high-frequency (0.150-0.500 Hz; HF) components and the LF/HF ratio of the HR spectral analysis. The LF spectral power was significantly lower in the supine position (P < 0.05) during ITP. Upright tilting was accompanied by a 22.6% reduction in HF values during the rest period, whereas in ITP the HF spectral power rose by 31.2% (P < 0.01) during tilt, characterizing a greater parasympathetic system control. Sympathetic control represented by the LF/HF ratio regressed markedly (P < 0.01) in response to the tilt test in ITP. CONCLUSIONS: The spectral analysis of SBP in the high frequencies shows that the changes in cardiac parameters are coupled with a decrease in sympathetic vasomotor control (-18%) and a reduction in diastolic pressure (-3.2%) in the response to the tilt test at the end of ITP. Spectral analysis could be a means of demonstrating impairment of autonomic balance for the purpose of detecting a state of fatigue that could result in overtraining.     

Effects of gender on the autonomic modulation of the cardiovascular responses to lower body negative pressure

BACKGROUND: The cardiovascular responses to submaximal lower body negative pressure (LBNP) appear to differ between genders, but the underlying mechanisms are uncertain. HYPOTHESIS: These differences are due to differences in the autonomic modulation of the cardiovascular system. METHODS: There were 14 women and 13 men who underwent LBNP to -50 mmHg in 10 mmHg increments of 6 min each. Heart rate (HR), stroke volume (SV), BP, forearm blood flow and R-R interval data were acquired. Spectral analysis of the R-R interval data was used to assess autonomic modulation with the low frequency component (LF) set at 0.04 to 0.15 Hz and the high frequency component (HF) at 0.15 to 0.4 Hz. RESULTS: The responses to LBNP to -40 mmHg did not differ between groups. LBNP of -50 mmHg evoked greater HR increases in the women than the men (7.2 +/- 1.0 vs. 3.8 +/- 1.1 bpm; p < 0.05), while SV, cardiac output and total peripheral conductance decreased more (-15 +/- 2 vs. -8 +/- 2 ml x beat(-1); -0.668 +/- 0.131 vs. -0.1778 +/- 0.124 L x min(-1); -0.009 +/- 0.002 vs. -0.004 +/- 0.001 units; p < 0.05). Normalized HF, an indicator of the vagal influence on HR variability, declined below rest at -40 mmHg while the LF/HF ratio, an indicator of sympathetic neural modulation of HR variability, increased above rest at -40 mmHg. These responses did not differ significantly between groups. CONCLUSIONS: These results suggest that gender differences in the cardiovascular responses to LBNP are not due to gross differences in modulation of the autonomic nervous systems.     

Effects of intermittent hypoxia on heart rate variability during rest and exercise

Changes in heart rate variability induced by an intermittent exposure to hypoxia were evaluated in athletes unacclimatized to altitude. Twenty national elite athletes trained for 13 days at 1200 m and either lived and slept at 1200 m (live low, train low, LLTL) or between 2500 and 3000 m (live high, train low, LHTL). Subjects were investigated at 1200 m prior to and at the end of the 13-day training camp. Exposure to acute hypoxia (11.5% O(2)) during exercise resulted in a significant decrease in spectral components of heart rate variability in comparison with exercise in normoxia: total power (p < 0.001), low-frequency component. LF (p < 0.001), high-frequency component, HF (p < 0.05). Following acclimatization, the LHTL group increased its LF component (p < 0.01) and LF/HF ratio during exercise in hypoxia after the training period. In parallel, exposure to intermittent hypoxia caused an increased ventilatory response to hypoxia. Acclimatization modified the correlation between the ventilatory response to hypoxia at rest and the difference in total power between normoxia and hypoxia (r (2) = 0.65, p < 0.001). The increase in total power, LF component, and LF/HF ratio suggests that intermittent hypoxic training increased the response of the autonomic nervous system mainly through increased sympathetic activity.     

Exercise training and autonomic nervous system activity in obese individuals

PURPOSE: This study was designed to investigate the effects of 12 wk of exercise training on autonomic nervous system (ANS) in 18 obese middle-aged men (N = 9) and women (N = 9) (age: 41.6 +/- 1.2 yr; BMI: 27.3 +/- 0.4 kg x m(-2); %fat: 29.6 +/- 1.3%, mean +/- SE). METHODS: Each subject participated in an aerobic exercise training at anaerobic threshold (AT), consisting of 30 min/session, 3 times/wk, for 12 consecutive weeks. The ANS activities were assessed by means of power spectral analysis of heart rate variability (HRV) at resting condition before, at 5 wk, and after the exercise program. RESULTS: The exercise training resulted in a significant decrease in body mass, BMI, and % fat (P < 0.01) but not in lean body mass (P > 0.05) together with a significant increase in the AT VO2 (P < 0.01). Our power spectral data indicated that there were significant increases in the low-frequency component associated with the sympathovagal activity (0.03--0.15 Hz, 348.5 +/- 66.8 vs 694.7 +/- 91.5 ms(2), P < 0.01), the high-frequency vagal component (0.15--0.4 Hz, 146.3 +/- 30.4 vs 347.7 +/- 96.5 ms(2), P < 0.05), and the overall autonomic activity as evaluated by total power (0.03--0.4 Hz, 494.8 +/- 88.5 vs 1042.4 +/- 180.9 ms(2), P < 0.01) of HRV after the training. CONCLUSIONS: Twelve weeks of exercise training has significantly improved both the sympathetic and parasympathetic nervous activities of the obese individuals with markedly reduced ANS activity, suggesting a possible reversal effect of human ANS functions. These favorable changes may also have an influence on the thermoregulatory control over the obesity.     

有晕厥史飞行员立位应激下自主神经功能评价

目的：评价加速度引起的意识丧失（G－LOC）或血管迷走性晕厥（VVS）飞行员在立位耐力试验（OTT）条件下自主遥作用。方法：对30例晕厥并阳 性OTT病例组（I组），20例晕厥并阴性OTT病例组（Ⅱ组）和15例年龄，性别，飞行机种，飞行时间相匹配的健康飞行员（对照组）的心率变异（HRV）和OTT的关系进行研究，对所测量OTT前后心率（HR），收缩压（SBP），舒张压（DBP）和HRV指标进行对比分析。结果：3组被试者OTT前平均HR，SBP，DBP比较无显著性差异（P＞0．05），OTT后I组HR明显高于其他两组（P＜0．01），SBP和DBP明显低于其他两组（P＜0．01），HRV指标中I组24h连续RR间期标准差（SDNN），HRV三角指数（HRVI），RR间期平均值（RR）明显小于其他两组（P＜0．01），平均1h 功率谱分析I组低频成分／高频成份比值（LF／HF）明显高于其他两组（P＜0．05），结论：晕厥并阳性OTT飞行员立位应激下交感神经张力增强，副交感神经张力减弱，使自主神经功能失调。     

跨时区飞行对飞行员心率变异性的影响

目的　探讨跨时区飞行对飞行员心率变异性的影响 ,以评价其对飞行员自主神经系统的作用。　方法　采用 2 4h动态心电图方法检测 16名跨时区国际长途飞行的飞行员动态心电图及心率变异性 (HRV) ;另外检测 10名国内昼间飞行的飞行员动态心电图及HRV作为对照。检查指标 :①HRV的低频功率 (0 .0 4～ 0 .15Hz ,LF) ;②HRV的高频功率 (0 .15～ 0 .4 0Hz,HF) ;③HRV的总频功率 (0 .0 4～ 0 .4 0Hz,TF)。计算飞行员HRV谱成份的夜间调节指数。用两组飞行员调节指数的差值作为自主神经负荷程度的定量估计。　结果　对照组飞行员的HF反映迷走神经活性在 2 4h中显示明显的昼夜节律 ,即夜间HF增高 ,LF降低 ;白天HF降低 ,LF增高。交感神经活性在跨时区飞行组上述谱成份的昼夜节律性明显降低。②对照组飞行员的HF夜间调节指数为 0 .32± 0 .11,而跨时区飞行组HF夜间调节指数为 0 .0 6± 0 .0 2 (P <0 .0 5 )。对照组LF夜间调节指数为 - 0 .0 2± 0 .0 8,而跨时区飞行组LF夜间调节指数为 - 0 .0 9± 0 .0 4 (P <0 .0 5 )。　结论　跨时区飞行使飞行员HRV谱成份的昼夜周期节律显著降低     

Effect of exercise intensity and repetition on heart rate variability during training in elite trotting horse

RR intervals of ten elite trotting horses were recorded during an interval training session performed on track. This study examined two hypotheses. Firstly, like in humans, the hyperpnea combined with a decrease in cardiac autonomic control on heart rate during heavy exercise could result in a prevalence of high frequency heart rate variability. Secondly, this prevalence could increase with the heavy exercise repetition. Two exercise intensities were compared: moderate (ME) and heavy (HE). Furthermore, heavy exercise repetitions were compared between the beginning and the end of the interval training session. When comparing ME and HE periods: heart rate was significantly lower (155 +/- 12 vs. 210 +/- 9 ms, p < 0.001), LF spectral energy (0.04 - 0.2 Hz) was significantly higher (ME: 6.94 +/- 4.80 and HE: 0.24 +/- 0.14 ms(2) . Hz (-1), p < 0.001) whereas HF (0.2 - 2 Hz) was significantly lower (ME: 7.09 +/- 2.24 and HE: 10.60 +/- 3.64 ms(2) . Hz (-1), p < 0.05). In relative terms, ME showed similar results in both LFn (LF/LF+HF) and HFn (HF/LF+HF) whereas HE showed a large prevalence of HFn energy compared to LFn (p < 0.001). The difference in LF/HF ratio between the two exercise conditions was significant (1.14 +/- 0.92 vs. 0.09 +/- 0.12, p < 0.001). Exercise repetition induced a significant increase in heart rate between the beginning and the end of the interval training session (207 +/- 10 beats . min (-1) vs. 212 +/- 9 beats . min (-1), p < 0.001) whereas LF energy decreases (1.54 +/- 1.65 vs. 0.32 +/- 0.24 ms(2) . Hz (-1), p < 0.01) and HF energy remained constant (10.79 +/- 4.10 vs. 10.40 +/- 3.35 ms(2) . Hz (-1), NS). This study confirmed the results observed in humans during heavy exercise conditions with a large prevalence of HF in contrast to LF, this prevalence increasing with exercise repetitions. The observed decrease in LF/HF ratio could provide an index of hyperpnea in horses during interval training.     

Autonomic adaptations in andean trained participants to a 4220-m altitude marathon

PURPOSE: Both training and chronic hypoxia act on the autonomic nervous system. Because trained Andean high-altitude natives could perform a high-altitude marathon (4220 m above sea level) in 02:27:23 h, we hypothesized that living in chronic hypoxia does not limit the training-induced benefits on the autonomic modulation of the heart. METHODS: Trained (N=13) and sedentary (N=11) Andean high-altitude natives performed an active orthostatic test. Eight of the trained subjects repeated the test 6-8 and 20-24 h after the end of a high-altitude marathon. Resting heart rate (HR) and the autonomic modulation of the heart were assessed by time domain and spectral analysis of HR variability (HRV): sympathetic (RR low frequency (LF)) and parasympathetic (RR high frequency (HF)) modulations, and sympathovagal balance (RR-LF:HF ratio). RESULTS: Trained subjects exhibited a higher total power of HRV and a lower resting HR (+30%, P<0.005) than sedentary subjects secondary to a higher and dominant parasympathetic modulation on sympathetic activity (RR-HF, RR-LF:HF ratio). At 6-8 h after the marathon, total power of HRV decreased (-69%), whereas resting HR increased from basal level (+22%), mainly because of a rise in sympathetic modulation (RR-LF, RR-LF:HF ratio). From 8 to 24 h of recovery, sympathetic modulation fell (RR-LF, RR-LF:HF ratio) and all HRV parameters were restored. Responses to the active standing position did not change between each recording session. CONCLUSION: Living in chronic hypoxia does not limit the training-induced benefits on the autonomic control of the cardiovascular system in Andean high-altitude natives. The sympathetic predominance on the heart observed 6-8 h after the high-altitude marathon disappeared after 1 d of recovery. Therefore, living at high altitude does not impair the autonomic response to training.     

Heart rate variability during high ambient heat exposure

INTRODUCTION: This study observed heart rate variability (HRV) measured in order to detect the changes in sympathovagal activity during high ambient (74 degrees C) temperature. HRV is a measure of heart rate (HR) fluctuations around the mean HR and has been used to indicate the balance between parasympathetic and sympathetic function of the autonomic nervous system in medicine and exercise, but not in extreme environments. METHODS: There were 10 healthy male subjects who wore Polar HR monitors (PE 5000) during a 15-min exposure (74.3 +/- 5.9 degrees C). RESULTS: HR increased significantly (p < 0.05) from 66.5 bpm pre-exposure to 106.0 bpm during exposure to the dry heat. A significant decrease in parasympathetic drive was indicated by: (1) a reduction of 89.1 +/- 31.3% in the proportion of interval differences between two normal R-R intervals that were in excess of 50 ms in length (pNN50); (2) an 83.4 +/- 7.0% decrease in the root mean square of successive R-R differences (RMSSD); and (3) an 82.7 +/- 11.4% decrease in the normalized high-frequency (HF norm) values. An increase in a sympathetic drive was indicated by a significant increase in: (1) the normalized low-frequency (LF norm) values of (84.5 +/- 19.4%); and (2) the LF:HF ratio (10.9 +/- 10.8%). DISCUSSION: The results from this study show that exposure to high ambient temperature produces a significant increase in HR through an increase in sympathetic and decrease in parasympathetic drive.     

Changes in cardiac autonomic activity during a passive 8 hour acute exposure to 5 500 m normobaric hypoxia are not related to the development of acute mountain sickness

Alterations in the autonomic nervous system after ascent to high altitude may be related to the development of acute mountain sickness (AMS). So far, the time course of cardiac autonomic modulation in relation to AMS development during the early hours at altitude is not well established. As AMS develops sometimes as early as 1 h and typically within 6 to 10 h at altitude, evaluating this time period provides information on cardiac autonomic responses with regard to AMS development. Prior studies exclusively investigated autonomic modulations in hypobaric hypoxia. Because barometric pressure per se might influence autonomic nervous system activity, the evaluation of cardiac autonomic alterations caused by hypoxia alone might give new insights on the role of the autonomic nervous system in AMS development. To assess the early responses of acute hypoxia on cardiac autonomic modulation and its association to the development of AMS, 48 male subjects were exposed for 8 h to acute normobaric hypoxia (FiO2 11.0%, 5?500 m respectively). Heart rate variability (HRV) was determined by 5-min recordings of successive NN-intervals in normoxia and after 2, 4, 6 and 8 h in hypoxia. Compared with normoxia, acute exposure to hypoxia decreased total power (TP), high frequency (HF) and low frequency (LF) components as well as the standard deviation of all NN intervals (SDNN), the root mean square of differences of successive NN intervals (rMSSD) and the proportion of differences between adjacent NN intervals of more than 50 ms (pNN50). LF:HF ratio, heart rate (HR) and blood lactate (LA) were augmented, indicating an increase in cardiac sympathetic activity. No differences were found between those who developed AMS and those who did not. Our results confirm reduced HRV with a shift towards sympathetic predominance during acute exposure to hypoxia. However, changes in cardiac autonomic modulations are not related to AMS development in acute normobaric hypoxia.     

Aerobic training and cardiovascular responses at rest and during exercise in older men and women

PURPOSE: The effects of an intense 8-wk aerobic training program on cardiovascular responses at rest and during exercise, including heart rate variability (HRV) as an expression of autonomic modulation, were evaluated in subjects over 70 yr (mean: 73.9 +/- 3.5 yr). METHODS: Before and after training in 7 men and 8 women: a) heart rate (HR), blood pressures (BPs), pulse pressure (PP), and oxygen uptake were measured at rest, during, and after exhausting incremental exercise; b) HRV power spectra were calculated at rest in supine and sitting, and during and after two submaximal constant loads (5 min). Power in low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, >0.15 Hz) bands were expressed as a percent of total power minus power < 0.04 Hz. RESULTS: After training: a) at rest HR and HRV parameters (in both body positions) were unchanged, whereas BPs decreased; b) peak cycle resistance and oxygen consumption increased by 25% and 18%, respectively, but no change in maximal HR and BPs were found; c) during submaximal loads HR was unchanged at the same metabolic demand, whereas SBP and DBP were lower than before at low loads whereas PP was unchanged. LF power decreased and HF increased at oxygen uptakes above about 0.7 L.min-1 similarly before and after training; and d) recovery of all parameters was similar to pretraining and complete after 10 min CONCLUSIONS: The increase in exercise capacity without changes in cardiovascular parameters suggests that 8 wk of aerobic training augmented peripheral gas exchange but not delivery to muscle. The lack of effect on HRV indicates that the improvements in aerobic power and cardiac autonomic modulation, at least in subjects over 70 yr, are dissociated. Moreover, the metabolic demand seems to be the main factor for the changes in HRV power spectra that occur during exercise.     

心率变异性分析的新指标及其在航空医学中的应用

目的通过对２４ｈ心率变异性（ＨＲＶ）谱成分极低频（ＶＬＦ）、低频（ＬＦ）与高频（ＨＦ）功率之间的关系进行回归分析，探讨回归方程各参数的病理生理意义及其在飞行员心功能鉴定中的价值。方法对象为健康女飞行员３０名、年龄相当的男飞行员３０名、可疑冠心病飞行员８例、确诊的冠心病人２０例。采用２４ｈ全信息动态心电图仪。分析指标：ＶＬＦ（０．００３Ｈｚ～０．００４Ｈｚ）、ＬＦ（０．０４Ｈｚ～０．１５Ｈｚ）、ＨＦ（０．１５Ｈｚ～０．４０Ｈｚ）和总体平均功率（０．００３Ｈｚ～０．４０Ｈｚ，ＴＦ），回归分析各频率间的关系，并进行ｔ检验。结果①ＶＬＦ和ＬＦ与ＨＦ均呈显著负相关；ＶＬＦ与ＨＦ的相关系数值（ｒ）显著大于ＬＦ与ＨＦ的相关系数值。②ＶＬＦ和ＬＦ与ＨＦ回归方程的斜率（Ｂ）、相关系数（ｒ）以及ＨＦ值均表现为夜间大于白天，女性大于男性，健康飞行员大于冠心病人。结论ＶＬＦ可能反映交感神经系统活性；ＶＬＦ或ＬＦ与ＨＦ回归方程的斜率可反映交感神经系统与副交感神经系统的均衡性，相关系数可反映二者的拮抗性与协调性。女飞行员的夜间迷走神经活性高于男性飞行员；冠心病人可表现有交感神经系统与副交感神经系统的协调性降低，以及迷走神经活性受损     

Autonomic adaptations to intensive and overload training periods: a laboratory study

PURPOSE: Looking for practical and reliable markers of fatigue is of particular interest in elite sports. One possible marker might be the autonomic nervous system activity, known to be well affected by physical exercise and that can be easily assessed by heart rate variability. METHODS: We designed a laboratory study to follow six sedentary subjects (32.7 +/- 5.0 yr) going successively through 2 months of intensive physical training and 1 month of overload training on cycloergometer followed by 2 wk of recovery. Maximal power output over 5 min (Plim5'), VO(2) and standard indices of heart rate variability were monitored all along the protocol. RESULTS: During the intensive training period, physical performance increased significantly VO(2peak) : +20.2%, < 0.01; Plim5': +26.4%, < 0.0001) as well as most of the indices of heart rate variability (mean RR, Ptot, HF, rMSSD, pNN50, SDNNIDX, SDNN, all < 0.05) with a significant shift in the autonomic nervous system toward a predominance of its parasympathetic arm (LF/HF, LFnu, HFnu, < 0.01). During the overload training period, there was a stagnation of the parasympathetic indices associated to a progressive increase in sympathetic activity (LF/HF, < 0.05). During the week of recovery, there was a sudden significant rebound of the parasympathetic activity (mean RR, HF, pNN50, rMSSD, all < 0.05). After 7 wk of recovery, all heart rate variability indices tended to return to the prestudy values. CONCLUSION: Autonomic nervous system status depends on cumulated physical fatigue due to increased training loads. Therefore, heart rate variability analysis appears to be an appropriate tool to monitor the effects of physical training loads on performance and fitness, and could eventually be used to prevent overtraining states.     

平行秋千摆动刺激中的心率变异分析

目的 观察飞行员在平行秋千摆动前、中、后反映心脏植物神经调节功能的心率变异性（ＨＲＶ）特点,搪塞以此评价线性加速度作用下前庭＝植物神经反应性的可能性。方法记录３７名飞行员在秋千摆动前、中、后的连续心电图,进行频率谱分析并计算低频成分（ＬＦ）和高频成分（ＨＦ）之幽会对被试者中ＬＦ／ＨＦ值在不同摆动阶段变化类型及分布耐受摆动时间的关系进行初步分析。结果 摆动中的ＬＦ明显降低,ＨＦ明显增高,ＬＦ／ＨＪＦ     

Effects of aerobic exercise training on 24 hr profile of heart rate variability in female athletes

BACKGROUND: The aim of this study was to investigate the effects of exercise training on autonomic regulation of heart rate under daily life conditions. METHODS: Twenty-six healthy female athletes (age 24.5 +/- 1.9 yrs) involved in regular physical activity were recruited during a period of yearly rest and randomly assigned to a five-week aerobic exercise training program (n = 13) or to a non-exercise control group (n = 13). MEASURES: Before and after the five-week training, all subjects underwent a bycicle ergometer stress test and a 24-hour dynamic ECG monitoring. Autonomic regulation of heart rate has been investigated by means of both time and frequency domain analyses of heart rate variability (HRV). Spectral analysis of R-R interval variability (autoregressive algorithm) provided markers of sympathetic (low frequency, LF, 0.10 Hz) and parasympathetic (high frequency, HF, 0.25 Hz) modulation of the sinus node. RESULTS: Trained subjects showed a reduced heart rate response to submaximal workload. Before training there was no significant difference between the two groups. After training resting heart rate did not significantly differ between trained and untrained subjects. No significant differences were observed in the different time domain indexes of heart rate variability. The day-night difference in SD and SDRR were significantly less in the trained as compared to the untrained group. Normalized LF and HF components did not significantly differ between trained and untrained subjects, during the awake period. The decrease in the LF and the increase in the HF component during nighttime were significantly less in the trained group. The LF/HF ratio was significantly decreased during the night in the untrained group whereas it was not significantly different from the awake state in the trained group. CONCLUSIONS: These findings of the relative night-time increase in LF and the decrease in the day-night difference in time domain indexes of heart rate variability suggest that, in young female athletes, exercise training is able to induce an increase in the sympathetic modulation of the sinus node which may coexist with signs of relatively reduced, or unaffected, vagal modulation.     

Rate of reduction of heart rate variability during exercise as an index of physical work capacity

Breathing rates during physical exercise suggest that, during these conditions, the high-frequency (HF) bandwidth of heart rate variability (HRV) analysis should be extended beyond conventional guidelines. However, there has been little investigation of the most appropriate choice of HF bandwidth during exercise. HRV analysis was performed in 10 males and six females during progressive bicycle exercise. Cardiac cycle (RR) interval and breath-by-breath respiratory data were simultaneously recorded. HRV powers were determined for the band-limited ranges 0.04-0.15 Hz [low-frequency (LF)], 0.15-0.4 Hz (HF 0.4) and 0.15-bf Hz (HF bf, where bf represents maximum breathing frequency). Mono-exponential functions described the relationship between HRV and work rate for each bandwidth (r=0.92-0.95) and were used to calculate the "HRV decay constant" (work rate associated with a 50% reduction in HRV power). The HRV decay constants for each bandwidth were linearly related to maximal work rate (r>0.71; P<0.001) and were substantially greater in males than in females (P<0.001). There was a significant difference between the HRV decay constants for HF 0.4 and HF bf (P<0.005) in both genders. The HRV decay constants for the LF and HF bf bandwidths appear to provide an indication of work capacity from submaximal exercise, without prior assumption regarding heart rate and its relationship with work rate.